One of the basic problems in remodelling is the quantification and mechanism of mineral and collagen conservation. The interaction of mineral with collagen and how this interaction relates to their conservation and destruction are not understood at this time. The objective of these studies is to investigate the mechanism of how the body handles mineral and mineralized collagen at a physiological and biochemical level during various treatments and ages. We have developed procedures that will aid in elucidating the turnover of mineral and collagen under normal and pathological conditions in young and adult animals. The experimental design is to quantify the turnover of old and accumulation of new minerals and mineralized collagen in chronically labeled animals over intervals of time after labeling when the animal has reached a steady state, isotopically and biologically. Since the phenomena of calcium loss and calcium conservation, and collagen loss and collagen reutilization are both known to exist, these studies should help to estimate the relative proportion between destructive and non-destructive bone turnover. Quantitative kinetics will be done in normal and PTX animals for: 1. vitamin 1,25-D3 deficient and toxic states; 2. parathyroid deficient and toxic states; 3. EDTA infusion; 4. calcium infusion; 5. effect of aging on bone remodelling.